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teamvmg

Can I make pre-preg with West?

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If I wet out lengths of carbon uni/biax with West System 105/205 epoxy, roll them up and put them in the fridge - will they last a couple of days?

 

What sort of temperature is needed?

 

I will need to be careful that the rolled up material does not start to exotherm before I get it cooled, the rolls will be about 400mm x 15m

 

Would 206 make any difference?

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If I wet out lengths of carbon uni/biax with West System 105/205 epoxy, roll them up and put them in the fridge - will they last a couple of days?

 

What sort of temperature is needed?

 

I will need to be careful that the rolled up material does not start to exotherm before I get it cooled, the rolls will be about 400mm x 15m

 

Would 206 make any difference?

 

I do not know if the curing will stop if you put them in the fridge but I doubt that the epoxy will be absorbed into the carbon/glass. I believe that it will still be as messy and sticky when you take them out.

 

Try "POLPREG" Take plastic film 0,2 mm thick and put that on a table roll out your fiber and wet it out with the resin you prefer to use, apply the resin with a roller and remove all air with a metal roller and put another plastic film on top. Start to cut your pieces by free hand or use a template made of suitable paper or cardboard depending on your table size you can make a big number of really advanced pieces of fiber still easy to cut with a pair of scissors. Put the cut out pieces in a pile and start to use them, they will be very easy to apply once you have removed the bottom plastic film and when you are happy with the location remove the cover plastic film and the fiber will drape nicely over even difficult shapes with very nice result. I do not know if this will help but it surely have solved my fearblink.gif of applying fiber in the roof or at the bottom of the hull.

 

//FOPtongue.giftongue.gif

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I do not know if the curing will stop if you put them in the fridge but I doubt that the epoxy will be absorbed into the carbon/glass. I believe that it will still be as messy and sticky when you take them out.

 

Try "POLPREG" Take plastic film 0,2 mm thick and put that on a table roll out your fiber and wet it out with the resin you prefer to use, apply the resin with a roller and remove all air with a metal roller and put another plastic film on top. Start to cut your pieces by free hand or use a template made of suitable paper or cardboard depending on your table size you can make a big number of really advanced pieces of fiber still easy to cut with a pair of scissors. Put the cut out pieces in a pile and start to use them, they will be very easy to apply once you have removed the bottom plastic film and when you are happy with the location remove the cover plastic film and the fiber will drape nicely over even difficult shapes with very nice result. I do not know if this will help but it surely have solved my fearblink.gif of applying fiber in the roof or at the bottom of the hull.

 

//FOPtongue.giftongue.gif

 

This is what I do also - works great. The only way to do tricky little stuff or really big stuff without getting covered in resin

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I do not know if the curing will stop if you put them in the fridge but I doubt that the epoxy will be absorbed into the carbon/glass. I believe that it will still be as messy and sticky when you take them out.

 

Try "POLPREG" Take plastic film 0,2 mm thick and put that on a table roll out your fiber and wet it out with the resin you prefer to use, apply the resin with a roller and remove all air with a metal roller and put another plastic film on top. Start to cut your pieces by free hand or use a template made of suitable paper or cardboard depending on your table size you can make a big number of really advanced pieces of fiber still easy to cut with a pair of scissors. Put the cut out pieces in a pile and start to use them, they will be very easy to apply once you have removed the bottom plastic film and when you are happy with the location remove the cover plastic film and the fiber will drape nicely over even difficult shapes with very nice result. I do not know if this will help but it surely have solved my fearblink.gif of applying fiber in the roof or at the bottom of the hull.

 

//FOPtongue.giftongue.gif

 

This is what I do also - works great. The only way to do tricky little stuff or really big stuff without getting covered in resin

 

this is what I do too. The fridge will definitely extend your goop life, though I don't know why you need it a couple days in advance. Maybe an hour or so. Also, rolling up the wet fabric with dry plastic either side will shift the plastic, wrinkle the fibers, prob make the goop get in places it didn't need to. You can roll it and still make it go flat again if your timespan is short and you're vac bagging; next day - not so much.

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There are resins out there that are designed for making your own pre-pregs. Sicomin do a system called SIPREG and wont cure untill you take the temperature up. cant say ive used it just chatted so the uk distributors (www.matrix-uk.com) about it when i was buying some othere stuff. good luck!!

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I've never made pre-preg, but I have had the discussions with people much much smarter than I (which is not a stretch) ~ Some fundamental requirements for making pre-preg are:

 

Good fiber wet out

getting a gel at a certain temperature and holding it there

reducing drain out (see gel above)

and hitting a cure temperature that is less than the Tg of most core materials - read: when you cook your preg, you don;t want your core to go to much.

 

The chemistry around pre-preg is pretty cool - you get much higher thermal properties out of the laminate based on the glue mix, but you have to keep it cold or the stuff with kick to the B state (B State = initial cure that is as brittle as a dock wife's vanity)

 

So to get good fiber wetout, your glue would have to be of low enough viscosity to encapsulate the fibers, but not too low that is runs out during gel up or initial cure -

 

Getting a good gel sets the glue in place and limits the tackiness of the laminate, thus increasing the ability to work with the stuff - but knowing where the sweet spot temperature wise is tricky if you are doing it yourself - The chemists can get a close calculation of where that temperature is based on their potion's mix - but you may be hard pressed to get that info out of a manufacturer ~

 

Lastly, after the initial room temp cure to the B State, that stack will need to be post cured to get all the components to react and cross link thus resulting in a stiff, strong, and tough composite - BUT!! If the mix is such that it requires a really high temperature to post cure to achieve that performance then you might a have screwed yourself if you are using a foam core - most PU/PVC/PET cores are good to approximately 200-250F (I did not fact check that - so please do your homework before laying shit up) -So if your homemade pre-preg needs need 300F to post cure and your foam cores is only good to 200-250F, guess what - that foam no longer be foam and that smile will go to frown really quick ~

 

WEST System epoxies are designed to achieve 90-95% of their physical performance at a room temperature cure - If you are the kind of user that can post cure and needs a more technical epoxy system, you can check out PRO-SET ( prosetepoxy.com ) ~ and yes someone bought an add ;)

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I do not know if the curing will stop if you put them in the fridge but I doubt that the epoxy will be absorbed into the carbon/glass. I believe that it will still be as messy and sticky when you take them out.

 

Try "POLPREG" Take plastic film 0,2 mm thick and put that on a table roll out your fiber and wet it out with the resin you prefer to use, apply the resin with a roller and remove all air with a metal roller and put another plastic film on top. Start to cut your pieces by free hand or use a template made of suitable paper or cardboard depending on your table size you can make a big number of really advanced pieces of fiber still easy to cut with a pair of scissors. Put the cut out pieces in a pile and start to use them, they will be very easy to apply once you have removed the bottom plastic film and when you are happy with the location remove the cover plastic film and the fiber will drape nicely over even difficult shapes with very nice result. I do not know if this will help but it surely have solved my fearblink.gif of applying fiber in the roof or at the bottom of the hull.

 

//FOPtongue.giftongue.gif

 

This is what I do also - works great. The only way to do tricky little stuff or really big stuff without getting covered in resin

 

this is what I do too. The fridge will definitely extend your goop life, though I don't know why you need it a couple days in advance. Maybe an hour or so. Also, rolling up the wet fabric with dry plastic either side will shift the plastic, wrinkle the fibers, prob make the goop get in places it didn't need to. You can roll it and still make it go flat again if your timespan is short and you're vac bagging; next day - not so much.

 

I tried making my own west 105 prepreg as well - but have only tested it on a patch so far. I did some reading onthe interwebs and I guess I was mainly worried about what was the gel stage was so I played with the lftovers in the plastic cup untill it started getting stiff - so that it wouldnt drip off my stirring stick. I place the patch between 2mil poly and popped in the freezer (missus is used to this, just desnt like the collection of insects daughter and I collect). Took the patch out the next weekend and heated it on the bench on top of the polly sheet with a 100 W bulb over it. Bench got warm/hot to the touch but I dont know how hot, I guess 55-60C. polly wrikld a bit so wasnt flat but Resin set nicely. I have no way to tell how stiff this patch is, as I stupidly didnt do a control experiment (set a similar patch in the normal way). I'd be really happy if someone could do the experiments let us know how to detemine the home made prepreg entry to the gel stage, which I take --read-- is the safe time to place in the freezer..

 

I was thinking just roll the material up with aluminum foil on the top layer to conduct some cool into the roll. I didt think about the wrinkling, I guess youcould us a large radius.

stupid Dick

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I do not know if the curing will stop if you put them in the fridge but I doubt that the epoxy will be absorbed into the carbon/glass. I believe that it will still be as messy and sticky when you take them out.

 

Try "POLPREG" Take plastic film 0,2 mm thick and put that on a table roll out your fiber and wet it out with the resin you prefer to use, apply the resin with a roller and remove all air with a metal roller and put another plastic film on top. Start to cut your pieces by free hand or use a template made of suitable paper or cardboard depending on your table size you can make a big number of really advanced pieces of fiber still easy to cut with a pair of scissors. Put the cut out pieces in a pile and start to use them, they will be very easy to apply once you have removed the bottom plastic film and when you are happy with the location remove the cover plastic film and the fiber will drape nicely over even difficult shapes with very nice result. I do not know if this will help but it surely have solved my fearblink.gif of applying fiber in the roof or at the bottom of the hull.

 

//FOPtongue.giftongue.gif

 

This is what I do also - works great. The only way to do tricky little stuff or really big stuff without getting covered in resin

 

this is what I do too. The fridge will definitely extend your goop life, though I don't know why you need it a couple days in advance. Maybe an hour or so. Also, rolling up the wet fabric with dry plastic either side will shift the plastic, wrinkle the fibers, prob make the goop get in places it didn't need to. You can roll it and still make it go flat again if your timespan is short and you're vac bagging; next day - not so much.

 

I tried making my own west 105 prepreg as well - but have only tested it on a patch so far. I did some reading onthe interwebs and I guess I was mainly worried about what was the gel stage was so I played with the lftovers in the plastic cup untill it started getting stiff - so that it wouldnt drip off my stirring stick. I place the patch between 2mil poly and popped in the freezer (missus is used to this, just desnt like the collection of insects daughter and I collect). Took the patch out the next weekend and heated it on the bench on top of the polly sheet with a 100 W bulb over it. Bench got warm/hot to the touch but I dont know how hot, I guess 55-60C. polly wrikld a bit so wasnt flat but Resin set nicely. I have no way to tell how stiff this patch is, as I stupidly didnt do a control experiment (set a similar patch in the normal way). I'd be really happy if someone could do the experiments let us know how to detemine the home made prepreg entry to the gel stage, which I take --read-- is the safe time to place in the freezer..

 

I was thinking just roll the material up with aluminum foil on the top layer to conduct some cool into the roll. I didt think about the wrinkling, I guess youcould us a large radius.

stupid Dick

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This is second hand info so please treat it accordingly:

an experienced composite part builder told me that you might encounter problems with humidity in the laminate if you put homemade prepregs with a plastic film on both sides into your fridge.

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My thinking has been that 105 is stiff enough that no gelling is required

 

I have been pre laminating carbon tapes with 105/205 up to about 7 meters long, rolling them up without any layers in between and then using them straight away to wind around a mandril. I am going to chuck one in the freezer and see if it is useable, if the bloody thing cooks off, I gonna need to buy the wife a new freezer

 

Dick - are you using 205 or 206

 

Quasi - would sealing the roll in a bag stop the change in humidity?

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This is second hand info so please treat it accordingly:

an experienced composite part builder told me that you might encounter problems with humidity in the laminate if you put homemade prepregs with a plastic film on both sides into your fridge.

 

This is very true, when pre-preg materials are put in the freezer you must ensure it is in a sealed bag to prevent any excess moisture from the air getting in to the bag and settling on the fibre as frost. when it is removed it is essential to allow the material to reach room temperature to prevent condensation from forming. This moisture when in a laminate under vacuum will expand as temperature increases the water will turn to steam (remember under full vacuum water will boil at 36 Celsius)creating voids in your final part. A great deal of external pressure (vacuum pressure is not enough, in fact full vacuum can make these voids bigger) is required to collapse these voids and is the reason autoclaves are used to cure composites.

 

Most pre-preg resins are b staged and as such are wax like at room temperature this prevents the resin running all over the place but still allows the material to have drape and tack which is why room temp cure resins in my opinion are not suitable to make pre-pregs. I have noticed that low temperature cure pre-pregs generally display greater tack at room temperature than say a 180 C cure pre-preg does, and have never heard of a room temperature cure pre-preg (not saying they don't exist just that I haven't heard of them) I would assume that they would be a nightmare to handle due to tack and resin flow, and if you could handle them they wouldn't flow enough to allow entrapped air to escape via a vacuum path. It would also mean the working time with the pre-preg would be very short, generally pre-pregs have an outlife of 10-30 days.

 

hope some of this helps

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@vmg

Yes I used fast hardener that gets me about 30 mins or more on the cloth as a thin layer. I read that you had to get the resin catalysts to gel stage before you cool it to stop it hardning. So I let my experiment get thick enough in the mixing cup so that it was just at the stage it wouldnt drip off the mixing stick. If I rotated the mixing stick it would sag though -- so not set and not drippy- was my def of b stage.

 

Then I bunnged it in the freezer to stop the resin reaction. I don't recall if the piece was runny but I was trying to get it to the stage like leather so I guess i has it just before it was like leather. -- I dint want it to set so prempted how far I should let it go. Once the sheet is cool it just won't set. If you keep it under (ask Vegas) degrees C it will happily rest. So I guess you would take your material out of the freezer and pop into the 4C fridge compartment to let it thaw but not get above the ask Vegas temp. This goes a long way to prevent condensation unless you are in n carolina in the afternoon in summer.

 

I have been caught out with fast hardener before when making too many layers at one time. Goes off quicker than you are ready an exothern ruins core. So I would be wary of rolling it until you got the resin/fiber layup under the "ask Vegas" temperature. Once under that it's doest make a runaway reaction so you sould be able to roll it up no problemo dudeo right? that's why I was thinking about foil to help keep the heat down if I rolled it. Imagine having a solid expensive carbon door stop if you screw that operation up.

 

My idea of ideal way to make your own RT prepreg would to arrange some steel tabletop to work on but attach copper tubes underneath in zigzag pattern so you could pump ice cold water to cool the table top after the resin was leathery- kinda like concrete slab heating heating but in reverse. Once the thin layer was cool just roll it up and throw it in freezer for long term storage.

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If using vacc to consolidate the fibers this getting it to the gel stage i was striving for might be counter productive really. Runny at RT might be the go because you do want to get rid of excess resin and air. So all the same materials and breather as wet layup are still needed

 

If using pressure to consolidate them naybe carefully applied and rolled out b sstage ppreg is good.

 

For me it was just about convenience, planning a large area layup without any help. I was hoping to get all the glass resined and cooled and ready to apply then allow it to warm under vacc to set and post cure.

 

In the end I just got more helpers. One of whom brought beer!!!

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That's pretty much my train of thought now. Vegas and you other guys are throwing up so many variables and areas for cock-ups, I had better stay in my comfort zone and be confident in what I build

 

I get these ideas while alone in the shed. It's good to be able to chuck them in here, without doing the uresearch , to get feedback without too much piss-taking from the experts( remember the 'whats the breaking strain of carbon' thread!)

Thanks guys

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Quick litle google nets this http://www.woodward-...er-prepreg.html

 

 

OK, ignorant question:

 

He ends up with much lower resin content than typical for vacuum-bagging.

 

What he is doing, to summarize quickly, is squeegeeing the resin while the fabric is on plastic sheets, then later using these resin-impregnated sheets on or in a mold and autoclaving while vacuum-bagging, if I understand correctly.

 

So why does he end up with less resin?

 

Because the vacuum-bagging is being done at elevated temperature, and possibly pressure? Is that really the entirety of it? If so, is the temperature relevant (perhaps from allowing curing at reduced viscosity) or really just the pressure, if he is using pressure?

 

In that case, wouldn't the resin content be the same if squeegeeing the resin onto the fabric already on the mold, if desired? If so, then the point of doing the sheets in this manner is entirely convenience, where more convenient?

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